chore(project): update to karma>=4

* Use createPriorityPreprocessor instead of deprecated createPreprocessor API
* Bump node version to 8+

BREAKING CHANGES:

* requires karma >= 4
* requires NodeJS >= 8

lib/preprocessor.js

@@ -4,20 +4,11 @@ var preprocessor = require('karma/lib/preprocessor');
 var os = require('os-shim');
 var path = require('path');
 
-var api = ['config.preprocessors', 'config.basePath', 'injector'];
-
-
-function arrayEquals(a, b) {
-  return a.join('#') === b.join('#');
-}
-
-
 function getPreprocessorFactory() {
+  var factory = preprocessor.createPriorityPreprocessor;
 
-  var factory = preprocessor.createPreprocessor;
-
-  if (!arrayEquals(factory.$inject, api)) {
-    console.log('incompatible karma preprocessor: found', factory.$inject, 'expected', api);
+  if (factory.$inject[0] !== 'config.preprocessors') {
+    console.log('incompatible karma preprocessor: the first parametr should be config.preprocessors but', factory.$inject[0]);
     throw new Error('incompatible karma preprocessor');
   }
 
@@ -31,15 +22,14 @@ function getPreprocessorFactory() {
 
 var originalFactory = getPreprocessorFactory();
 
-var createPreprocessor = function(config, basePath, injector) {
-
+var createPreprocessor = function(config, ...args) {
   // add our preprocessor for .browserify.js files
   config[path.resolve(os.tmpdir(), '*.browserify.js')] = ['browserify-bundle'];
 
-  return originalFactory(config, basePath, injector);
+  return originalFactory.apply(null, [config, ...args]);
 };
 
-createPreprocessor.$inject = api;
+createPreprocessor.$inject = originalFactory.$inject;
 
 
 // publish patched preprocessor